we hit a brick wall because someone thinks this is too much work or whatever.

I'd like you to take a moment to ask yourself why you don't implement this feature, since you clearly want it. Even if you don't know PHP, it isn't a difficult language to learn. Could it be because it is too much work?

Asking somebody else to create software isn't different from asking somebody else to paint your house. Painting a house isn't a complicated task, it's not very difficult or very demanding and it only takes a few days. Yet, you don't usually see people ask strangers to come paint their house; That would be ludicrous.

Your best bet to turning this RFC into reality is to find other users who are interested in it and pool your resources (time and/or money) to develop it yourselves.

Any news on this implementation for 3.2? Putting excuses for not implementing it is not helpful. Many users really forget their usernames and they must be allowed to login via email without cumbersome extensions not even present on the Extension database.

You seriously think that downloading an extension, unzipping it, then putting it in the ext folder and enabling it in the ACP is cumbersome (there doesn't seem to be anything more to this extension)?

Currently there are absolutely no plans to add this into 3.2 right now as it is in maintenance mode, meaning new features won't be added to it unless it is to resolve a security issue. If someone puts in the work then it would be in the next version. Kindly start thinking about the suggestions given to you by the other code contributors to move forward your desire to have this in the core.